1. Field of the Invention
The invention relates to a biodynamic roller skate having a shoe with a sole located on the shoe, with front rollers which form a rolling surface and which are located in the forefoot area in sole, and with rear rollers which form a rolling surface and which are located in the rear foot area in sole.
2. Description of Related Art
From the published German Patent Application DE-A-28 21 644 on which the invention is based, a roller skate is known which is used not only in sports, but also is used for therapeutic treatment of muscle or bone deformations, and especially posture injuries to legs or feet. These posture injuries to the feet can, among others, be attributed to overly low training of the musculature of the feet.
Also, European Patent Application No. 0710 495 discloses a roller skate of the initially mentioned type in which the front sole section has a plurality of rollers to support the forefoot. This roller skate can be used not only in sports, but can also be used for therapeutic treatment when muscle or bone deformations and especially posture injuries to legs or feet occur. These posture injuries to the feet can among others be attributed to overly low training of the musculature of the feet. However, tests with the aforementioned roller skate have shown that it does not yet optimally imitate and support the natural progression of motion of the foot when walking.
In a healthy foot, the weight of the body is distributed on the foot proceeding from the hip joints via the knee down to the ankle joint. A healthy foot without anatomical deformations is loaded when standing with between 50% and 90% of the entire load on the heel bone and with between 10% and 50% of the entire load on the middle and forefoot area. When walking, the force which is distributed by the legs on the ankles is dynamically distributed on the forefoot. A healthy foot is, therefore, kept permanently under load by biodynamic equilibrium which is produced by the shape of the individual foot bones and by muscle traction.
Roughly 70% of the population has a so-called pes planovalgus deformity. Causes thereof are congenital weakness of the connective tissue, lack of foot training, continual walking on a hard floor and continual walking in hard shoes. The pes planovalgus deformity occurs in small children and is especially pronounced in adults. As is shown in FIG. 4a, the normal deviation of the rear foot axis from the vertical is from 0.degree. to 6.degree.. For pes planovalgus, this rear foot axis, however, deviates by more than 6.degree. from the vertical, deviations of 10.degree., as is shown in FIG. 4b, with deviations of up to even 20.degree. being possible. As a result of the inward inclination of the rear foot, the longitudinal arch of the foot also settles, by which a classical fallen arch is formed in which, while standing, almost the entire lower surface of the foot is in contact with the ground.
As a therapeutic measure in early childhood, pes planovalgus is counteracted with foot-gymnastic exercises. They include exercises in walking on tiptoes and walking on the heels, gripping exercises and extension exercises in the toe area. This previous pes planovalgus therapy by remedial gymnastic exercises generally comprises exercising once to several times a week with a remedial gymnastic therapist and furthermore daily exercising at home. However, these exercises have the disadvantage that they are not kept up over several years, on the one hand, the parents not having the necessary stamina, and on the other hand, the children themselves enjoy the exercises so little that, for this reason, due to resistance behavior caused thereby, further exercising is made impossible.
Another therapeutic measure for improving the arch of the foot is to provide tailored inserts. They are generally re-ordered semi-annually from the physician depending on the growth state of the foot and support the arch of the foot during the growth phase. This therapy is, however, a passive measure and does not promote the muscle growth responsible or co-responsible for the deformity, but in contrast allows the musculature to rest since the arch of the foot is additionally supported by the inserts.
As a therapeutic measure the roller skate mentioned initially can also be used since skating with roller skates, on the one hand, provides training for the leg and foot musculature, and on the other hand, provides interesting recreation for the children so that this therapy is also maintained over a longer time period.
The roller skates known from published German Patent Application Nos. DE-A-28 21 644, DE-A-23 04 853 and DE-A-22 50 201, and German Utility Model No. DE-U-87 11 944, have rigid soles. They inadequately consider the necessity of using the foot as a complicated organ for control. Instead, they are controlled essentially from thigh and the lower leg musculature. In particular, they do not allow selective loading of individual segments of the foot.
A roller skate is known (published German Application No. DE-B-1 117 013) in which the rollers are mounted by being inserted directly into the foot plate of the shoe which consists of the sole and heel. The foot plate consists of two parts which are interconnected via a center articulated area in a longitudinally adjustable manner, specifically a sole and a heel. Each part has a projecting flexible slide element which overlaps the two slide elements and are connected by an attachment screw, thus forming the articulated area. Thus, there is a flexible center sole section between the sole and heel. The skater moving with this roller skate, therefore, experiences a rolling motion in the foot which is similar to ordinary walking or running.
Also, this known roller skate with a flexible middle sole section has not yet been able to satisfy all requirements of therapeutic treatment of the pes planovalgus deformity in completed studies. That is, the vertical swivelling capacity of the rollers and the flexibility of the parts lead to a rather undefined progression of motion. The front rollers which are arranged on the corners of an equilateral triangle aligned symmetrically to the longitudinal axis of the roller skate cannot satisfactorily simulate the natural rolling behavior of the foot.
Finally, from the aforementioned general prior art of roller skates, it is known, of course, that in the rear foot area of the roller skate there can be a braking device with brake shoes which strike the road in order to allow active braking by the user.